It is known to use rotary valves to control the air supply from medical air pumps to provide compressed air in a specific sequence, to an inflatable device, for example an air mattress or a compression garment.
In most rotary valves, the provision of compressed air in a specific sequence is determined by ports and channels built into two parts, the rotor and the stator, that rotate relative to each other. The rotor and stator are discs of suitable solid material that are held together by spring force with flat mating faces forming an airtight seal.
As the rotor rotates relative to the fixed stator, different ports in the mating faces of the two parts are connected together and so vary the routing of compressed air through the valve. The porting is designed and made to follow the desired sequence of inflation for the inflatable device.
The sequence of port connections can be quite ingenious, but as the required sequence becomes more complex a large diameter valve is required which is costly and difficult to manufacture requiring a high torque motor to drive it. Furthermore, a design with more complex porting results in limited separation between the ports leading to inaccuracies and air leaks.